HYDROLOGIC OUTLOOK
Warning Issue Date: 529 AM CST WED DEC 23 2009
FLOODING RESULTING FROM SIGNIFICANT RAINFALL...ALONG WITH
SNOW MELT AND ICE JAMS...POSSIBLE WEDNESDAY AND THURSDAY...
A PRODIGIOUS LOW PRESSURE SYSTEM WILL BRING THE POSSIBILITY OF
FLOODING TO CENTRAL AND ESPECIALLY SOUTHERN IOWA THROUGH THURSDAY
EVENING. PRECIPITATION TYPE WILL BE A MAJOR DRIVING FORCE IN THE
FLOODING THREAT. AREAS OF FREEZING RAIN AND DRIZZLE ARE POSSIBLE
TODAY AND TONIGHT OVER CENTRAL PORTIONS OF THE AREA...WITH
GENERALLY RAIN AND ISOLATED THUNDERSTORMS EXPECTED OVER FAR
SOUTHERN IOWA. RAINFALL AMOUNTS OF A HALF INCH TO NEARLY TWO
INCHES ARE ANTICIPATED THROUGH THURSDAY NIGHT.
THE COMBINATION OF ABOVE FREEZING TEMPERATURES...ALONG WITH
SEASONALLY MODERATE TO HEAVY RAINFALL...WILL LEAD TO A POTENTIALLY
SIGNIFICANT AMOUNT OF SNOW MELT AND RUNOFF INTO AREA STREAMS.
LOCALIZED FLOODING MAY ALSO OCCUR IN OTHER AREAS...SUCH AS URBAN
AREAS...WHERE THE DRAINAGE SYSTEMS MAY BE IMPAIRED DUE TO SNOW AND
ICE CLOGGED INTAKES.
ANOTHER CONCERN IS BREAK UP ICE JAMS ON AREA RIVERS. ESTIMATED RIVER
ICE DEPTHS RANGE FROM 2 INCHES IN SOUTHEAST IOWA...TO 6 INCHES IN
CENTRAL IOWA. THE RUNOFF WILL LIKELY BE ENOUGH TO BREAK UP THE ICE
ESPECIALLY AS ONE MOVES SOUTHWARD. SINCE THE RIVER ICE IS
RELATIVELY THIN...THOUGH...ONLY MINOR...LOCALIZED PROBLEMS DUE TO
ICE JAMS ARE EXPECTED.
RIVERS MOST LIKELY TO BE AFFECTED INCLUDE THE CHARITON...DES
MOINES RIVER FROM DES MOINES DOWNSTREAM...AS WELL AS THE SOUTH
SKUNK...CEDAR CREEK...AND THE THOMPSON RIVERS. OTHER SMALLER
STREAMS AND CREEKS MAY ALSO BE AFFECTED.
KEEP CURRENT ON THE LATEST FORECASTS...INCLUDING POSSIBLE WATCHES
AND WARNINGS.
$$
PODRAZIK/ZOGG
WINTER STORM WATCH
Warning Issue Date: 104 PM CST WED DEC 23 2009
...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 3 PM CST THIS
AFTERNOON...
...WINTER STORM WATCH REMAINS IN EFFECT FROM THURSDAY AFTERNOON
THROUGH FRIDAY EVENING...
A WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 3 PM CST THIS
AFTERNOON. A WINTER STORM WATCH REMAINS IN EFFECT FROM THURSDAY
AFTERNOON THROUGH FRIDAY EVENING.
...WINTER WEATHER ADVISORY...
* SHORT TERM TRENDS...AN AREA OF RAIN IS LIFTING NORTH AND
BEGINNING TO DIMINISH OVER THE NEXT FEW HOURS. UP TO A TENTH OF
ICE MAY ACCUMULATE WILL HAVE ACCUMULATED BEFORE THE FREEZING
RAIN CHANGES TO RAIN. LESS THAN AN INCH OF SNOW IS ALSO
EXPECTED THROUGH THAT TIME.
...WINTER STORM WATCH...
* LONG TERM TRENDS...THE PRECIPITATION SHOULD SWITCH TO MAINLY
RAIN LATE TONIGHT AND EARLY THURSDAY BEFORE TRANSITIONING BACK
TO A WINTRY MIX AND EVENTUALLY ALL SNOW LATE THURSDAY. ONCE IT
DOES THE SNOW MAY BE HEAVY AND WIND BLOWN...ESPECIALLY INTO
FRIDAY WHEN WINDS INCREASE.
* STORM TOTAL SNOW ACCUMULATIONS...BY THE TIME THE PRECIPITATION
DIMINISHES SATURDAY...THREE TO SIX INCHES OF SNOW IS EXPECTED.
* WINDS...BRISK EAST WINDS OF 15 TO 25 MPH WILL BE COMMON TODAY
INTO THURSDAY. BY FRIDAY...WINDS WILL BECOME NORTHWEST AT 25
TO 35 MPH WITH HIGHER GUSTS.
* VISIBILITY...DURING THE PERIODS OF HEAVIER SNOW LATE THURSDAY
AND FRIDAY...VISIBILITIES WILL GENERALLY BE LESS THAN ONE MILE
AND EVEN DOWN TO A QUARTER MILE DURING THE HEAVIEST SNOWS.
WITH INCREASING WINDS AND SNOW COINCIDENT BY FRIDAY...BLOWING
SNOW AND GREATLY REDUCED VISIBILITIES NEAR BLIZZARD CONDITIONS
ARE POSSIBLE.
* IMPACTS...TRAVEL WILL BECOME INCREASINGLY DIFFICULT IN THE
WATCH AREA ON ON CHRISTMAS EVE NIGHT AND CHRISTMAS DAY AS SNOW
ACCUMULATES AND WINDS INCREASE. IN THE HEAVIEST SNOW AREAS...
TRAVEL MAY BECOME NEARLY IMPOSSIBLE DUE TO BLOWING AND
DRIFTING SNOW THURSDAY NIGHT INTO FRIDAY.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A WINTER WEATHER ADVISORY MEANS THAT PERIODS OF SNOW...SLEET...OR
FREEZING RAIN WILL CAUSE TRAVEL DIFFICULTIES. BE PREPARED FOR
SLIPPERY ROADS AND LIMITED VISIBILITY...AND USE CAUTION WHILE
DRIVING.
A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.
$$
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